1 files changed, 131 insertions, 0 deletions
diff --git a/rest_framework/metadata.py b/rest_framework/metadata.py
new file mode 100644
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--- /dev/null
+++ b/rest_framework/metadata.py
@@ -0,0 +1,131 @@
+"""
+The metadata API is used to allow cusomization of how `OPTIONS` requests
+are handled. We currently provide a single default implementation that returns
+some fairly ad-hoc information about the view.
+
+Future implementations might use JSON schema or other definations in order
+to return this information in a more standardized way.
+"""
+from __future__ import unicode_literals
+
+from django.core.exceptions import PermissionDenied
+from django.http import Http404
+from rest_framework import exceptions, serializers
+from rest_framework.compat import force_text, OrderedDict
+from rest_framework.request import clone_request
+from rest_framework.utils.field_mapping import ClassLookupDict
+
+
+class BaseMetadata(object):
+    def determine_metadata(self, request, view):
+        """
+        Return a dictionary of metadata about the view.
+        Used to return responses for OPTIONS requests.
+        """
+        raise NotImplementedError(".determine_metadata() must be overridden.")
+
+
+class SimpleMetadata(BaseMetadata):
+    """
+    This is the default metadata implementation.
+    It returns an ad-hoc set of information about the view.
+    There are not any formalized standards for `OPTIONS` responses
+    for us to base this on.
+    """
+    label_lookup = ClassLookupDict({
+        serializers.Field: 'field',
+        serializers.BooleanField: 'boolean',
+        serializers.CharField: 'string',
+        serializers.URLField: 'url',
+        serializers.EmailField: 'email',
+        serializers.RegexField: 'regex',
+        serializers.SlugField: 'slug',
+        serializers.IntegerField: 'integer',
+        serializers.FloatField: 'float',
+        serializers.DecimalField: 'decimal',
+        serializers.DateField: 'date',
+        serializers.DateTimeField: 'datetime',
+        serializers.TimeField: 'time',
+        serializers.ChoiceField: 'choice',
+        serializers.MultipleChoiceField: 'multiple choice',
+        serializers.FileField: 'file upload',
+        serializers.ImageField: 'image upload',
+    })
+
+    def determine_metadata(self, request, view):
+        metadata = OrderedDict()
+        metadata['name'] = view.get_view_name()
+        metadata['description'] = view.get_view_description()
+        metadata['renders'] = [renderer.media_type for renderer in view.renderer_classes]
+        metadata['parses'] = [parser.media_type for parser in view.parser_classes]
+        if hasattr(view, 'get_serializer'):
+            actions = self.determine_actions(request, view)
+            if actions:
+                metadata['actions'] = actions
+        return metadata
+
+    def determine_actions(self, request, view):
+        """
+        For generic class based views we return information about
+        the fields that are accepted for 'PUT' and 'POST' methods.
+        """
+        actions = {}
+        for method in set(['PUT', 'POST']) & set(view.allowed_methods):
+            view.request = clone_request(request, method)
+            try:
+                # Test global permissions
+                if hasattr(view, 'check_permissions'):
+                    view.check_permissions(view.request)
+                # Test object permissions
+                if method == 'PUT' and hasattr(view, 'get_object'):
+                    view.get_object()
+            except (exceptions.APIException, PermissionDenied, Http404):
+                pass
+            else:
+                # If user has appropriate permissions for the view, include
+                # appropriate metadata about the fields that should be supplied.
+                serializer = view.get_serializer()
+                actions[method] = self.get_serializer_info(serializer)
+            finally:
+                view.request = request
+
+        return actions
+
+    def get_serializer_info(self, serializer):
+        """
+        Given an instance of a serializer, return a dictionary of metadata
+        about its fields.
+        """
+        if hasattr(serializer, 'child'):
+            # If this is a `ListSerializer` then we want to examine the
+            # underlying child serializer instance instead.
+            serializer = serializer.child
+        return OrderedDict([
+            (field_name, self.get_field_info(field))
+            for field_name, field in serializer.fields.items()
+        ])
+
+    def get_field_info(self, field):
+        """
+        Given an instance of a serializer field, return a dictionary
+        of metadata about it.
+        """
+        field_info = OrderedDict()
+        field_info['type'] = self.label_lookup[field]
+        field_info['required'] = getattr(field, 'required', False)
+
+        for attr in ['read_only', 'label', 'help_text', 'min_length', 'max_length']:
+            value = getattr(field, attr, None)
+            if value is not None and value != '':
+                field_info[attr] = force_text(value, strings_only=True)
+
+        if hasattr(field, 'choices'):
+            field_info['choices'] = [
+                {
+                    'value': choice_value,
+                    'display_name': force_text(choice_name, strings_only=True)
+                }
+                for choice_value, choice_name in field.choices.items()
+            ]
+
+        return field_info